I don't want to over-react to this, but this could be a paradigm shift for planetary geological models. I thought the polar instability was important to the hypothesis for redistributing ice to mid latitudes.

There really are a lot of geomorphic features on Mars that resemble glacial features on earth, and the concept that Martian glaciers sublimated rather than melted adds a new twist to the picture. I remember seeing images returned in the mid 70's that made me think of periglacial processes.

The problem I am having with this, is that I didn't think there was enough mobile water available on Mars to build significant, mid-latitude glaciers. I may have been imagining the Martian system to be simpler than it really is. The mass movement of large quantities of volatiles from the poles to more equatorial regions might help propagate axial wanderings.

This is an amazing planet, and we are just beginning to appreciate the diversity of the processes at play. We need to focus our efforts on understanding one of our sister planets in this solar system. Sorry about the rant, but the amazing observations coming down from our stretched planetary exploration missions continue to amaze me.

These features could also be mud flows, muddy terrains slowly creeping like glaciers. Do not forget that, if liquids cannot exist on the surface, they can exist underground, forming watertables and muddy layers. Only some metres of terrain are enough to provide the pressure necessary to maintain liquid water, and some metres more to maintain liquid carbon dioxid.

Also, as several already noted, the wandering of martian rotation axis may play an important role in Mars geology and climatology. Given the intensity of eolian erosion on Mars (able to invert features like large craters, implying an ablation of hundred of metres) we may wonder where all this dust goes. Logical reply: the dust is mixed with frozen ice in the polar cap. And when the rotation axis moves, it left glaciers, layered deposits, and the traces lake what is in discution in this thread. Very likely these linear deposits (together with the layered deposits) are made of loess, finely grained rock dust, which does not turn to earth like on Earth.

This one known as the "Inca city" is really astonishing. My explanation is that this very ancient impact filled with molten lava some faults into a sandy terrain. There are many other such features.

QUOTE (CosmicRocker @ Oct 19 2005, 03:36 AM)

Interesting idea... How much overburden would be required to provide enough pressure to depress the melting point of buried ice and create mud flows?

1000 bars, or about 10kms deep on Mars, makes water freeze at -10°C, the lowest possible temp for pure liquid water. So this alone cannot explain the massive mud flows observed into many places. To explain this we must invoke geothermal heating, or liquid carbon dioxid, the later can turn to liquid at only 4 bars, some tens of metres deep on Mars. The most common hypothesis is that there are huge layers of sand/dust on Mars, soaked with a mixture of water and carbon dioxid, the whole think frozen and solid like rock. But the undermost parts can turn liquid, from geothermal heating, pressure, or eutectic mixing, resulting into large outbursts of mud or liquids. For instance a volcanic emanation of carbon dioxid could pervade water ice and turn it liquid, much like salt does.

This one known as the "Inca city" is really astonishing. My explanation is that this very ancient impact filled with molten lava some faults into a sandy terrain. There are many other such features.1000 bars, or about 10kms deep on Mars, makes water freeze at -10°C, the lowest possible temp for pure liquid water. So this alone cannot explain the massive mud flows observed into many places. To explain this we must invoke geothermal heating, or liquid carbon dioxid, the later can turn to liquid at only 4 bars, some tens of metres deep on Mars...

The latitude of some features are at around 40°N. Surface temperatures can approach 0°C here. Then you only have to worry about having sufficient over pressure for liquid water. Only a few centimeters of soil is required for this.

The latitude of some features are at around 40°N. Surface temperatures can approach 0°C here. Then you only have to worry about having sufficient over pressure for liquid water. Only a few centimeters of soil is required for this. Bob Clark

General measurements show that water must be frozen at great depth (hundred of metres, or kilometres) all around Mars. This is because, even if in some places and times the temperature can be positive, the average is alway much lower than zero. So there is a thick layer of frozen ground, called permafrost. There is even at the very surface a thin layer (around one metre) of completely dessicated ground, due to the fact that Mars air is very dry. But all this of course does not avoid liquid water to exist locally and intermitently on the surface, if there is a cause which drives water out of the ground, or if there is a thick enough layer of snow or ice.

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